High-temperature creep resistant alloy



Patented Sept. 7, 1954 HIGH-TEMPERATURE CREEP RESISTANT ALLOY Samuel R. Callaway, Huntington Woods, and Fred J. Webbere, Royal Oak, Mich., assignors to General Motors Corporation, Detroit, Mich.,

a corporation of Delaware No Drawing. Application January 27, 1951,

Serial No. 208,245

8 Claims.

This invention has to do with an improved high temperature creep resistant alloy.

The alloy of our invention is particularly adapted for parts which must withstand high stresses under elevated temperature conditions up to 1600 F., be resistant to oxidation at temperatures up to 2000 F. and at the same time have a relatively high ductility. Illustrative examples of parts for which our alloy is especially adapted are turbine blades or buckets and nozzle diaphragm vanes for gas turbines.

In common forms of high temperature alloys, creep resistance is obtained at the expense of ductility and lack of ductility is frequently an imposing limitation on an otherwise promising alloy.

Our new alloy is of nickel base and contains a minimum of strategic materials. It combines exceptional creep resistance at temperatures up to 1600 F. with good ductility.

The high temperature creep resistant alloy in accordance with our invention preferably consists essentially as follows:

0.10 to 0.20% carbon 0.25% maximum manganese 0.75% maximum silicon 13.00 to 17.00% chromium 4.00 to 6.00% molybdenum 1.50 to 3.00% titanium 2.00 to 4.00% aluminum 0.01 to 0.10% boron 8.00 to 12.00% iron Balance nickel While the foregoing is the preferred composition of the alloy of the present invention, some variation in the amounts of the several constituents is permissible without departing from the principles of the invention. For example in certain applications it is contemplated the carbon may be omitted entirely and in others may be as high as 0.25%.

Boron has a powerful effect on the alloy. By increasing the boron content above 0.10% the creep strength at elevated temperature is increased and the ductilitydecreased. Advantage may be taken of the increase in creep resistance at elevated temperature resulting from a higher boron content within the limits imposed by the ductility requirement in the particular application. In general the boron may range from about 0.01 to about 0.5%.

It is contemplated also that the maximum amounts of silicon and manganese may be increased to as high as about 1% for specific applications. The aluminum content may be decreased to as low as about 1% for some applications.

The following are illustrative examples of typical alloys in accordance with our invention and showing the results of tests thereon:

Emample I Test specimens were made by precision casting into investment molds an alloy melted in an induction furnace consisting essentially as follows: 0.15% carbon, 0.08% manganese, 0.30% silicon, 15.0% chromium, 4.63% molybdenum, 11.6% iron, 3.23% aluminum, 2.91% titanium, 0.02% boron, balance nickel.

Test specimens of this material were subjected to a static tensile load of 24,250 pounds per square inch at a test temperature of 1500 F. It took 680 hours under these test conditions to elongate the test specimen 1% and 805 hours to rupture the test specimen. Impact resistance at room temperature on unnotched Charpy specimens was 28 to 36 foot pounds. A similar test on the alloy of Example I except that a temperature of 1600 F. was employed and a static tensile load of 25,000 pounds per square inch showed a cree life of 40 hours with 3.70% elongation at rupture. The time to produce 1% creep was 32 hours.

Example II Test specimens were made by precision casting an alloy composed of 0.12% carbon, 0.09% manganese, 0.35% silicon, 15.5% chromium, 4.75% molybdenum, 10.6 iron, 2.85 aluminum, 2.51 titanium, 0.024% boron, and the balance nickel. Impact resistance at room temperature on unnotched Charpy specimens was 34 to 42 foot pounds. A test bar of this material was fatigue tested at a temperature of 1500 F. under a static tensile stress of 24,250 pounds per square inch and a dynamic bending stress of plus or minus 19,250 pounds per square inch. In other words, the stress repeatedly varied during the test from 5000 to 43,500 pounds per square inch. The loading varied 180 times each second. After 284 hours the bar had only elongated /2%. The test was discontinued after 307 hours and the bar appeared in good condition. When the test was discon tinued the bar had elongated 0.69. A similar fatigue test was made on the alloy of Example 11 except that a temperature of 1600 F. was used. It took 30 hours under these conditions to elongate the bar 1% and 42 hours to rupture the bar. The percentage elongation at rupture was 3.75.

Example III ganese, 0.47% silicon, 14.6% chromium, 4.98%

3 molybdenum, 10.1% iron, 2.20% aluminum, 2.71% titanium, 0.02% boron and the balance nickel. Impact resistance at room temperature on unnotched Charpy specimens was 34 to 44 foot pounds.

A test specimen of this material was subjected to a static tensile load of 24,250 pounds per square inch at a temperature of 1500 F. It took 186 hours under these test conditions to elongate the test specimen 1% and 221 hours to rupture the test specimen. The percentage elongation of the test specimen at rupture was 2.28.

Example IV Test specimens were made by precision casting an alloy composed of 0.14% carbon, 0.12% manganese, 0.43% silicon, 14.6% chromium, 4.72% molybdenum, 11.5% iron, 2.89% aluminum, 2.52% titanium, 0.122% boron and the balance nickel. Impact resistance at room temperature on unnotched Charpy specimenswas 22 to 30 foot pounds. A test specimen made of this material was subjected to a static tensile load of 24,250 pounds per square inch at a temperature of 1600 F. It took 50 /2 hours under these test conditions to elongate the test specimen 1%. The test was discontinued after 64 hours and the test specimen appeared in good condition. The percentage elongation at the time of discontinuance of the test was 3.75. Another test specimen made of this same material was fatigue tested. The part was fatigue tested at a temperature of 1600 F. under the loading conditions referred to above in connection with Example II. It took 20 hours under these test conditions to elongate the test specimen 1% and 37% hours to rupture the same. The percentage elongation at rupture was 4.25.

The alloy or alloys of our invention may be compounded or made up in any desired manner. Any desired melting furnaces may be used. Typical examples of melting furnaces which have been used are the indirect arc and induction types. Protective atmospheres preferably are employed during the melting operation. It is preferable also to employ protective atmospheres in the molds in which the material is cast. Mold materials may be those employed for conventional high temperature alloys.

Various changes and modifications of the embodiments of our invention described herein may bev made without departing from the spirit and principles of the invention.

We claim:

1. A nickel base alloy exhibiting in the as cast condition a stress-rupture life of at least about 221 hours when subjected to a static tensile load of 24,250 pounds per square inch at a temperature of 1500 F. and a percentage elongation at rupture of at least about 2.28, said alloy consisting essentially as follows:

0.0 to 0.25% carbon 0.0 to 1.00% manganese 0.0 to 1.00% silicon 13.00 to 17.00% chromium 4.00 to 6.00% molybdenum 1.50 to 3.00% titanium 1.00 to 4.00% aluminum 0.01 to 0.50% boron 8.00 to 12.00% iron Balance nickel.

2. A nickel base alloy exhibiting in the as cast condition a stress-rupture life of at least about 221 hours when subjected to a static tensile load of 24,250 pounds per square inch at a temperature of 1500 F. and a percentage elongation at rupture of at least about 2.28, said alloy consisting essentially as follows:

0.10 to 0.20% carbon 0.25% maximum manganese 0.75% maximum silicon 13.00 to 17.00% chromium 4.00 to 6.00% molybdenum 1.50 to 3.00% titanium 2.00 to 4.00% aluminum 0.01 to 0.10% boron 8.00 to 12.00% iron Balance nickel.

0.15% carbon 0.08% manganese 0.30% silicon 15.0% chromium 4.63 molybdenum 1 1.6 iron 3.23% aluminum 2.91% titanium 0.02% boron Balance nickel.

4. A nickel base alloy exhibiting in the as cast condition a stress-rupture life of at least about 221 hours when subjected to a static tensile load of 24,250 pounds per square inch at a temperature of 1500 F. and a percentage elongation at rupture of at least about 2.28, said alloy consisting essentially as follows:

0.12% carbon 0.09% manganese 0.35% silicon 15.5% chromium 4.75% molybdenum 10.6% iron 2.85% aluminum 2.51 titanium 0.024% boron Balance nickel.

5. A nickel base alloy exhibiting in the as cast condition a stress-rupture life of at least about 221 hours when subjected to a static tensile load of 24,250 pounds per square inch at a temperature of 1500 F. and a percentage elongation at rupture of at least about 2.28, said alloy consistingessentially as follows:

0.15% carbon 0.06% manganese 0.47% silicon 14.6% chromium 4.98% molybdenum 10.1% iron 2.20% aluminum 2.71% titanium 0.02% boron Balance nickel.

6. A nickel base alloy exhibiting in the as cast condition a stress-rupture life of at least about 221 hours when subjected to a static tensile load of 24,250 pounds per square inch at a temperature of 1500 F. and a percentage elongation at rupture of at least about 2.28, said alloy consisting essentially as follows:

0.14% carbon 0.12% manganese 0.43% silicon 14.6% chromium 4.72% molybdenum 11.5% iron 2.89% aluminum 2.52% titanium 0.122% boron Balance nickel.

7. A high temperature creep resistant alloy consisting as follows:

0.0 to 0.25% carbon 0.0 to 1.00% manganese 0.0 to 1.00% silicon 13.00 to 17.00% chromium 4.00 to 6.00% molybdenum 1.50 to 3.00% titanium 1.00 to 4.00% aluminum 0.01 to 0.50% boron 8.00 to 12.00% iron Balance nickel.

8. A high temperature creep resistant alloy consisting as follows:

6 0.10 to 0.20% carbon 0.25% maximum manganese 0.75% maximum silicon 13.00 to 17.00% chromium 4.00 to 6.00% molybdenum 1.50 to 3.00% titanium 2.00 to 4.00% aluminum 0.01 to 0.10% boron 8.00 to 12.00% iron Balance nickel.

References Cited in the file of this patent UNITED STATES PATENTS Number Number Name Date Rohn et a1 June 17, 1941 Scott et al July 2, 1946 Franks et a1 July 4, 1950 Bieber et al. Oct. 9, 1951 Guy Nov. 20, 1951 FOREIGN PATENTS Country Date Great Britain Oct. 26, 1945 Great Britain Mar. 29, 1949 OTHER REFERENCES Guy, Treatise in Trans. of Amer. Soc. for Metals, vol. 41, 1949, pages -140. 

1. A NICKEL ALLOY EXHIBITING IN THE AS CAST CONDITION A STRESS-RUPTURE LIFE AT LEAST ABOUT 221 HOURS WHEN SUBJECTED TO A STATIC TENSILE LOAD OF 24,250 POUNDS PER SQUARE INCH AT A TEMPERATURE OF 1500* F. AND A PERCENTAGE ELONGATION AT RUPTURE OF AT LEAST ABOUT 2.28, SAID ALLOY CONSISTING ESSENTIALLY AS FOLLOWS: 0.0 TO 0.25% CARBON 0.0 TO 1.00% MANGANESE 0.0 TO 1.00% SILICON 13.00 TO 17.00% CHROMIUM 4.00 TO 6.00% MOLYBDENUM 1.50 TO 3.00% TITANIUM 1.00 TO 4.00% ALUMINUM 0.01 TO 0.50% BORON 8.00 TO 12.00% IRON BALANCE NICKEL. 